1) Field of the Invention
This invention relates to an output power controlling apparatus and method for an internal combustion engine for reducing a vibration (acceleration shock) upon pedaling of an accelerator pedal or a vibration (shift shock) upon speed changing operation.
2) Description of the Related Art
Generally, a vibration (acceleration shock) is generated upon pedaling of the accelerator pedal of an automobile (particularly upon sudden pedaling of the accelerator pedal). Such an acceleration shock arises from the fact that the engine torque changes suddenly in response to sudden pedaling of the accelerator pedal and a torsional vibration is generated in the driving system by the sudden change of the engine torque. Such a torsional vibration of the driving system as just mentioned appears as a vibration phenomenon of the vehicle body in the forward and backward direction.
As a countermeasure for suppressing such a vibration of a driving system generated in response to an operation of the accelerator pedal as described above, a method of opening the throttle slowly is known widely. This method, however, degrades the acceleration feeling. Also, another method for suppressing such a vibration as described above is known wherein a compensator (inverse filter) W(s) of an inverse function to an inherent transmission characteristic between the throttle opening and the driving torque [in other words, a model Gp(s) of a vehicle on which a vibration is excited] is provided as shown in FIG. 17 and this pre-compensator is used to control the throttle opening to suppress the torsional vibration and improve the responsibility.
Also, a two-stage torque inputting method is known wherein a stepwise input signal (accelerator opening variation) is inputted at two separate stages.
However, the prior art methods described above individually have subjects to be solved. In particular, the method which employs the inverse filter W(s) has a subject that, although a vibrational component of the output can be canceled, where the model Gp(s) of the vehicle is complicated, it is difficult to set an optimum inverse filter W(s). Meanwhile, the two-stage torque inputting method is not suitable for practical use because the target value must usually be known although some effect can be achieved for suppression of a vibration as seen from FIG. 18.
Incidentally, Japanese Patent Laid-Open No. 2001-132501 discloses an apparatus which detects a specific vehicle state amount and detects a rotational frequency component of a vehicle driving system included in the specific vehicle state amount and then changes the engine torque or the transmission gear ratio based on the detected rotational frequency component to suppress the vibration.
However, since the apparatus detects a specific vehicle state amount, it is necessary to take the displacement between a timing at which the state amount is generated and the timing at which a control adjustment amount originating from the generation of the state amount is outputted, that is, a period of dead time, into consideration. Thus, if it is tried to achieve a control process of a high degree of accuracy including the dead time, then a very heavy burden is imposed on the control processing apparatus, and this gives rise to a problem that it makes practical use of the apparatus difficult.